1. Field of the Invention
The invention pertains to the field of airborne antennas and more specifically to antennas mounted on a cylindrical metallic surface with limited extensions therefrom for radiating and receiving signals with very wide instantaneous bandwidths.
2. Description of the Prior Art
Constraints on antenna system design are determined by the instantaneous bandwidth of the radiated signal, the desired spatial distribution of that signal, the desired relation and reception efficiency, and dimensional limitations for a particular application. For cw or narrow band signals, design parameters to meet these objectives are generally well known. When the fractional bandwidth, however, becomes very wide (50% to 100%), only one or two cycles of the carrier exists within a radiation time interval and the narrow band approach to antenna design is no longer applicable. This wide signal bandwidth condition suggests quasi-optical or time delay techniques as effective antenna design procedures. Of the two techniques for designing antennas for wide bandwidth signals, the quasi-optical approach, wherein reflectors, lenses, and horns, though dispersive, are utilized to achieve the design objectives has found greater acceptance. In many applications, however, space constraints and the dispersive characteristics of the optical techniques establish the time delay technique as a more suitable approach.
The present invention utilizes time delay techniques to provide wide instantaneous bandwidth signal antennas mounted on a cylindrical metallic surface, such as the fuselage of a missile or small aircraft, that do not significantly extend above the surface.